The overall aim of our program is to explore and explain the differences that appear in the surfaces of cells following tumorigenic "transformation". We are interested in all the aspects of research in this area, but over the coming year will concentrate much of our attention on describing and explaining what happens to the surface of secondary chick embryo fibroblasts following transformation by Rous sarcoma virus. This system has already received detailed biological analysis. In addition, we are attracted by the availability of excellent temperature sensitive mutants and are actively engaged in studies with TS68, a mutant isolated by Hanafusa and coworkers. The specific problems we will be investigating in the near future are: 1) The decrease in concentration of three specific proteins following transformation. 2) The role of cell surface proteolysis in transformation. 3) The biophysical state of cell surface proteins and lipids. 4) The effects of transformation on glycoprotein structure. BIBLIOGRAPHIC REFERENCES: Synthesis of Glycolipids and Phospholipids in Hamster Cells: Dependence on Cell Density and the Cell Cycle. Hirschberg, C.B., Wolf, B.A., and Robbins, P.W. J. Cell Physiology 85:31 (1975). Decrease in Membrane Associated Actin of Fibroblasts Following Transformation by Rous Sarcoma Virus (tumor transformation, cellular actin, temperature sensitive virus). Wickus, G., Gruenstein, E., Robbins, P.W. and Rich, A. PNAS 72:746 (1975).